Diagnosis of numerical chromosome abnormalities is almost invariable based on the evaluation of mitotic chromosome compliments using chromosome banding to facilitate individual chromosome identification. Chromosome analysis has become a major diagnostic tool in many areas of medicine including obstetrics, hematology, oncology, and clinical genetics. Despite major advances in the field of cytogenetics the diagnosis of chromosome abnormalities remains a time-consuming and labor- intensive procedure performed by highly trained and skilled technologists. The objective of this research proposal is to test the feasability of developing a rapid DNA hybridization-based molecular cytogenetic test for the diagnosis of chromosomal syndromes. The test to be developed is based upon hybridization in situ of chromosome specific repetitive DNA probes to dividing or non- dividing cells and on the rapid and sensitive detection of diploidy or aneuploidy by immunofluorescence or histochemical techniques.